DNA hybridization detection by label free versus impedance amplifying label with impedance spectroscopy

We have successfully developed a DNA biosensor based on double layer capacitance variations due to DNA hybridization. The study was performed to demonstrate the feasibility of electrical detection of DNA hybridization using electrochemical impedance spectroscopy (EIS). At 100 Hz, electrochemical impedance measurements on a label-free DNA sensor show a 25% increase for dsDNA on a Au electrode compared with the same gold electrode with immobilized ssDNA. Differential experiments were carried out to establish the selectivity of the biosensor; no impedance change was observed at electrodes with non-specific DNA sites. An enzyme amplification scheme employing an impedance amplifying label (IAL) was developed to increase the sensitivity of the DNA sensor. In this approach, after hybridization, the enzymatic precipitation of an insoluble compound on the sensing interface causes a significant impedance change. The total impedance, again measured at 100 Hz, is 160% higher than the impedance with the label-free dsDNA on the electrode.